Process for producing high bulk stretch yarns



H. SERVAGE 3,333,469

PROCESS FOR PRODUCING HIGH BULK STRETCH YARNS Aug. 1, 1967 Original Filed April 19, 1963 INVENTOR.

HENRI SERVAGE @MZM United States Patent 3,333,409 PROCESS FOR PRODUCING HIGH BULK STRETCH YARNS Henri Servage, Cremieu, Isere, France, assignor to Mouliuage et Retorderie de Chavanoz, a corporation of France Continuation of application Ser. No. 274,118, Apr. 19, 1963. This application July 11, 1966, Ser. No. 565,055

5 Claims. (Cl. 57--157) This application is a continuation of application Ser. No. 274,118, filed Apr. 19, 1963, now abandoned.

It is widely known to produce highly crimped synthetic yarns called high-bulk yarns by the false-twist process, in which there is imparted to the yarn a false twist which is set before the untwisting, the highly crimped synthetic yarns thus obtained exhibiting considerable decrimping stretch. However, this deorimping stretch is not as high as that which can be obtained by the older discontinuous process, in which the yarns are overtwisted, set on bobbins and untwisted in succesive separate operations.

For some applications, not only is the value of this decrimping streach important, but also the rapidity with l which the yarn returns to the crimped state when the tension is removed. This decrimping rapidity, called instantaneous elastic recovery, performs an essential function in articles such as tights and swimsuits, and the conventional high-bulk yarns obtained by the discontinuous process are still very widely employed in their manufacture for this reason.

According to the invention, the stretch and instantaneous elastic recovery of highly crimped synthetic yarns called high-bulk yarns can be substantialy improved in the false-twist process by an extremely simple means, namely wetting, immediately upstream of the tube giving the false twist, and downstream of the heating element.

The wetting may be effected with hot or cold water which may contain a wetting agent and/ or an oiling agent, which may be in solution or in dispersion. An oiling treatment may equally be used.

The wetting or oiling facilitates the formation of the twist and regularizes the latter. It also facilitates the subsequent untwisting of the yarn and insures unsticking of any filaments which are struck by the pa-rtialy carbonized initial sizing oil, while softening and dissolving the residues formed. Consequently, the regularity of the dyeing aflinity is improved and the yarn is reconditioned. However, the most important result is a 10-20% increase in st-recth. The ,instantaneous elastic recovery, which is rather difficult to express in figures, but which is shown on the finished articles, is also substantially improved. In addition, such properties as crimp contraction, breaking strength, modulus, energy to break and the like are also substantially improved.

The wetting may be effected by contact with a semi-submerged roller or with a wick, by capillary, by spraying, dipping or any other equivalent means.

The invention will be more readily understood from the following practical examples, but it is to be understood that these have no limiting character, the invention including any variant Within the same spirit.

The drawing illustrates typical apparatus for the practice of this invention.

In the drawing, a yarn 1 unwound from a bobbin 2 re ceives a light tension from a tensioning member 3 and is fed forward by the rollers 4. 'It thereafter enters the heat ing element 5, in which it is heated, preferably by contact with a uniformly curved heating surface.

On leaving the heating element, the yarn comes into contact with a roller 6, which is wetted on the surface with an appropriate liquid, for example by contact with another roller, which is partially submerged in the wetting agent. Immediately afterwards, the wetted yarn enters the twister 7, in which it undergoes a, false twist, which extends backwards into the heating element, and is set at the outlet. After leaving the twister 7, the yarn is taken up by the rollers 8, of which the speed bears an appropriate ratio to that of the rollers 4, so as to permit the slight shrinkage usually aimed at between these rollers 8 and 4. The set yarn untwists downstream of the twister 7. The rollers 8 feed the yarn to the takeup spool 9, which is driven by the driven roller 10 and a reciprocating guide 11 effects the winding with the desired traverse. The winding speed on the spool 9 may be adjusted in relation to that of the rollers 8 in order to insure additional shrinkage. A second, known thermal treatment may take place between the rollers 8 and the guide 11 at heater 12. If desired, additional feed rolls can be substituted for reciprocating guide 11 to provide overfeed control.

The fol-lowing examples illustrate the best mode, as presently known, of performing the process of this invention. In each example, apparatus as shown in the drawing is utilized, except that a third pair of feed rolls is substituted for traverse guide 11 and heater 12 is not utilized. The measurements made are standard procedures for the Instron machine.

Example I Type 288 Du Pont nylon yarn, 70 denier-34-filament- /2 turn Z twist is passed through the apparatus with the heater temperature set at 225 C. and the twister spindle set at 72,000 revolutions per minute for imparting 71.5 turns per inch of S twist (as viewed from the top of the twister) in the yarn. Overfeed values between rolls 4 and 8, 8 and feed rolls substituted for traverse guide -11, and between these latter rolls and rolls 9 and 10 are, respectively, 5%, 5% and -2.3%.

As the yarn exists from the heater, it is contacted with a wick saturated with water. A control yarn is similarly treated except that the saturated wick is not employed.

The control yarn has a breaking strength of 310.4 grams compared to 338.2 grams for the yarn treated in accordance with this invention. The modulus of the control yarn is increased from 831.6 grams at elongation to 930.8 grams through use of the saturated wick. Furthermore, the percent stretch under a load of 100 grams is increased from 108.19% to 134.08% by the present invention. -In addition, the instantaneous elastic recovery is noticeably improved.

Example II The procedure of Example I is repeated except that the spindle is set to impart Z twist (as viewed from the top of the twister spindle). Yarn treated in accordance with this invention extends 48.68% before breaking, compared with a value of 42.12% for the control. The energy required to break the yarn of this invention is 429.7 inch grams compared with 362.4 for the control.

Example III The procedure of Example I is repeated except that the wick is saturated with Ortholube HT, a textile lubricating oil. The percent of contraction after relaxation in water at F. for the control, and oil treated yarns are, respectively, 64.33% and 67.43%. The modulus at 100% elongation is increased from 886.8 grams to 1016.5 grams as a result of the oil treatment. The percent stretch and instantaneous elastic recovery are also substantially increased by this treatment.

That which is claimed is:

1. A novel process comprising twisting a synthetic yarn in a substantially overfed condition, heat-setting the twist in said yarn at an elevated temperature, wetting said yarn during twisting and subsequent to heat-setting, and un- J twisting said yarn whereby it tends to return to its twisted configuration, said ya-rn thereby assuming a crimped configuration under relaxed conditions.

2. The process improvement of claim 1 wherein setting of the twisted yarn is effected by contact with a heated plate.

3. The process of claim 1 wherein the yarn is wetted with an aqueous medium.

4. The process of claim 3 further characterized in that the aqueous medium contains a wetting agent.

5. The process of claim 3 further characterized in that the aqueous medium contains an oiling agent.

References Cited UNITED STATES PATENTS FRANK I COHEN, Primary Examiner.

J. PETRAKES, Assistant Examiner. 

1. A NOVEL PROCESS COMPRISING TWISTING A SYNTHETIC YARN IN A SUBSTANTIALLY OVERFED CONDITION, HEAT-SETTING THE TWIST IN SAID YARN AT AN ELEVATED TEMPERATURE, WETTING SAID YARN DURING TWISTING AND SUBSEQUENT TO HEAT-SETTING, AND UNTWISTING SAID YARN WHEREBY IT TENDS TO RETURN TO ITS TWISTED CONFIGURATION, SAID YARN THEREBY ASSUMING A CRIMPED CONFIGURATION UNDER RELAXED CONDITIONS. 